There are numerous technologies available for inserting media into broadcast systems. For instance, public announcements generated as text may be added to a video broadcast signal (e.g., to notify viewers of technical difficulties, critical events, weather alerts, etc.). The scheduled program continues uninterrupted while an announcement text is displayed on the television screen. It is also possible to receive notification of a private event (such as receiving an e-mail) through a television screen. Notification may be generated as text and displayed on the television screen or may take the form of a recorded audio announcement.
More particularly, in recent years the development of Germany's Verkehrsfunk (known broadly in Europe) has allowed people who listen to tapes or CD's to receive important announcements, generally relating to traffic information, without having to continually listen to a specific station just because it happens to periodically announce traffic information for the area. The system makes it possible, by means such as a simple tone decoder, to turn on and off the audio insert. However, Verkehrsfunk has some limitations. For one, the announcement interruption always takes precedence over the play of the recorded medium. The system is often so simplistic that the recording does not even pause, but rather continues to play unheard while the announcement is spoken. The listener thus misses part of the recording. Moreover, the system uses a simple switch-over of the source selector of the amplifier, so the medium of the announcement and the medium of the recording (in this case, both audio) must be identical.
In addition, the event driving the switch-over happens in real time. That is, the signal arrives and the event itself creates the signal. For example, when the speaker starts to make a traffic information announcement he pushes a button that turns on a first pilot tone and at the end of the announcement he pushes another button that creates an end pilot tone.
In essence, to date the insertion of media into broadcast systems interrupts the broadcast stream. Moreover, prior systems are inefficient in that they require the user's medium of choice and the medium of the insertion to be of the same type.